US3112749A

US3112749A - Electric motor-driven pump arrangement for vacuum extraction apparatus for child-birth

Info

Publication number: US3112749A
Application number: US118798A
Authority: US
Inventors: Sokol Kurt
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-06-28
Filing date: 1961-06-22
Publication date: 1963-12-03
Anticipated expiration: 1980-12-03

Description

Dec. 3, 1963 K. soKol. 3,112,749

. ELECTRIC MOTOR-DRIVEN PUMP ARRANGEMENT FOR VACUUM ExTRAcTIoN APPARATUS FOR CHILD-BIRTH Filed June 22, 1961 s sheets-sheet 1 3,1 12,749 CEMENT FCR VACUUM EXTRACTION APPARATUS FOR CHILD-BIRTH Dec. 3, 1963 K. soKoL ELECTRIC MOTOR-DRIVEN PUMP ARRAN 5 Sheets-Sheet 2 Filed June 22, 1961 a @a m 71 Dec. 3, 1963 K. soKoL 3,112,749

ELECTRIC MOTOR-DRIVEN PUMP ARRANGEMENT FOR VACUUM EXTRACTION APPARATUS FOR CHILD-BIRTH Filed June 22, 1961 3 Sheets-Sheet 5 m ill 0 i fof? F/GJ /NvENroP A/urf Sov/(0L United States Patent C) 3,112,749 ELECTRC MOTOR-DRIVEN PUMP ARRANGE- MENT FOR VACUUM EXTRACTEQN APPA- RATUS EUR CHED-BHRTH Kurt Sokoi, 29S Schwachhauser Heerstrasse, Bremen, Germany Filed .inne 22, 1961, Ser. No. 113,798 Claims priority, application Germany June 28, 1960 18 Claims. (Cl. 1218-361) This invention relates to an electric motor-driven pump arrangement for vacuum extraction apparatus for childbirth, which automatically maintains a produced vacuum at a constant level.

In recent times the so-called vacuum extraction is used to an ever increasing extent for assisting delivery at childbirth. During the vacuum extraction a suction cup or pelotte is preferably placed on the head of the child and a vacuum is produced in the suction pelotte by means of a hand pump and can be controlled by means of a vacuum gauge. Instead of the hand pump, electric motor-driven pump arrangements are also used which automatically maintain the vacuum at a constant level. With the aid of the vacuum pelotte the child can then be extracted from the mothers womb.

It is the object of the invention to provide a pump arrangement which renders possible to a great extent a socalled blind change over of the vacuum applied.

This object is attained according to the invention by the provision of an electric motor-driven pump arrangement for vacuum extraction apparatus for child-birth, which comprises a suction pump, a hose conduit serving as a suction line and connected to said pump, parallel branch conduits leading from said hose conduit, controlling means arranged in said branch conduits for adjusting the apparatus to different Vacuum stages, and hand-adjustable needle Valves arranged in said branch conduits for the fine adjustment of the vacuum stages switched on.

According to one embodiment of the invention the controlling means for adjusting the apparatus to different vacuum stages are constructed as electropneumatic controlling means. Preferably, these controlling means cornprise magnetic valves which are arranged in each of the branch conduits and push-button switches are coordinated to the magnetic valves and provided with a mutually locking mechanism.

According to another embodiment of the invention the controlling means for adjusting the dii-ferent vacuum stages are constructed as purely mechanical controlling means. Preferably, these controlling means comprise a multiway-cock to which the branches of the hose conduit are connected. Conveniently, the multiway-cock has a plug which has a central bore communicating with the atmosphere and a hand wheel is provided by which the bore is adjustable to one of the branch conduits.

The pump arrangement preferably has three vacuum stages for producing diierent intensities of vacuum and a minimum vacuum stage which are formed by the branch conduits, and also a maximum vacuum stage, all branch conduits of the hose conduit being closed when switching on the maximum Vacuum stage.

The needle valves may be provided with hand wheels.

The pump arrangement may have an air vessel for sucking quickly or slowly, which vessel may be connected up with the hose conduit by an additional branch conduit, a needle valve with a hand wheel and a magnetic valve being arranged in the branch conduit and a tumbler switch being coordinated to the magnetic valve.

Signal lamps may be coordinated to the push-button switches for controlling the Vacuum stages or the multiway-cock, which lamps light up upon the operation of one of the switches or indicate the switching position of the mutliway-cock. In addition, two signal lamps may be coordinated to the push-button tumbler switch for switching the apparatus for rapid or slow suction, and another signal lamp may be arranged to indicate the switching on of the current supply and a further signal lamp may be arranged to indicate the maximum vacuum by means of a contact in a vacuum gauge. l

If necessary, a recording apparatus may be connected up with the vacuum extraction apparatus.

So as to be entirely independent of hand-manipulation, the controlling means may also be actuated by a footswitch arrangement. The foot-switch arrangement may comprise a foot-switch, a push-button switch being arranged in the foot-switch for each of the vacuum stages and for minimum and maximum vacuum stages and being arranged to transmit switching impulses via an electric circuit, and a locking device being provided for mutually locking the push-button switches in relation to each other.

The foot-switch arrangement may also comprise a footoperated tumbler switch, a foot pedal being arranged on the tumbler switch and switching contacts being coordinated to the vacuum stages and the stages for minimum and maximum Vacuum, the food pedal on being depressed actuating each time one of the switching contacts. The multiway-cock may be constructed as a foot-switch arrangement, a foot pedal being arranged on the footswitch arrangement for switching the multiway-cock to one of the branch conduits of the hose conduit and a locking device being arranged in the foot-switch arrangement for holding the toot-switch arrangement in the position actually adjusted. Finally the controlling means for switching the vacuum stages may be constructed as a hand-operated switch and arranged in the hose conduit close to the vacuum pelotte of the extraction apparatus.

The apparatus us a fully automatic apparatus may be provided with an additional switching arrangement which controls all the switching operations of the apparatus according to a previously set time table and which is arranged following the push-button switches or the multiway-cock and can be rendered inoperative by same.

Two preferred embodiments of a pump arrangement according to the invention will now be described by way of example and with reference tothe accompanying drawings, in which:

FIG. l is a perspective View, on a reduced scale, of a vacuum extraction apparatus provided with a first embodiment of the pump arrangement according to the invention;

FIG. 2 is a diagrammatic view, on a reduced scale, of a second embodiment of the pump arrangement;

FIG. 3 is a vertical section through the multiway-cock of the arrangement shown in FIG. 2;

FIG. 4 is a front elevation of a foot-switch with a plurality of push-button switches for the apparatus illustrated in FIG. l;

FIG. 5 is a side elevation of the foot-switch shown in FIG. 4;

FIG. 6 is a side elevation of a foot-operated tumbler switch for the apparatus shown in FIG. l;

FIG. 7 is a top plan View, partially in horizontal section, of the tumbler switch of FIG. 6;

FIG. 8 is a vertical section of a foot-operated tumbler switch for the apparatus illustrated in FIG. 2;

FIG. 9 is a horizontal section through the foot-operated tumbler switch illustrated in FIG. 8, and

FIG. 10 is a wiring diagram of the apparatus shown in FIG. l.

Referring now to FIG. 1, for the vacuum extraction a suction cup or pelotte 1 is used which is preferably made from a transparent synthetic plastic material. The suction pelotte 1 is connected by a flexible hose conduit 2 o with a handle 3 which is adjustable on a chain 4 attached to the base plate of the suction pelotte 1 and extending through the liexible hose conduit 2. After. the suction pelotte 1 has been placed on the head of a child, a pulling action is exerted on the handle 3 and transferred on to the child via the chain 4. A exible hose conduit 5 serving as a suction line extends from the handle 3, leads to a vacuum vessel 6 and thence to a suction pump 8 driven by an electric motor 7.

The apparatus illustrated in FIG. l is constructed as a desk cabinet 9. By means of a main push-button switch 10 the electric current can be switched on and ori. A lamp 12 provided on an upright desk panel 11 lights up when the apparatus is under current. On a desk panel 13 which is preferably arranged at an incline, not only the main switch 10 but also additional push-button switches 14, 15, 16 and 17 are mounted which are coordinated with

magnetic valves

18, 19, 20 and 21. These valves are provided in

branch conduits

22, 23, 24 and 25 of the hose conduit 5 which lead into the atmosphere. The magnetic valve 13 (minimum switching stage) coordinated with the switch 14 corresponds to the minimum suction effect and on being switched on enables so much air to be sucked from the atmosphere into the appertaining branch conduit 22 that the suction efect in the hose conduit 5 and the suction pelotte 1 is at its minimum. The switching on of the magnetic valve 19 (switching stage I) coordinated with the switch causes so much air to be sucked from the atmosphere into the branch conduit 23 that the suction effect in the suction pelotte amounts to about 0.2 to 0.3 atm. The switching on of the magnetic valve by means of the switch 16 (switching stage ll) causes a suction effect of about 0.4 to 0.5 atm. and the switching on of the magnetic valve 21 by means of the switch 17 (switching stage lll) causes a suction effect of about 0.6 to 0.8 atm. The maximum vacuum in the hose conduit 5 amounts to l atm. Normally a vacuum of about 0.6 to 0.8 atm, is used. The desk panel 13 also carries a push-button switch 25 with which no magnetic valve is coordinated (maximum 'switching stage). If the switch 26 is depressed, the full suction power of the pump 8 acts on the suction pelotte 1. The switches 14, 15, 15, 17 and 26 are provided with a mutual locking mechanism so that when one of these switches is depressed, the previously actuated switch automatically springs out and only one of the

magnetic valves

1S, 19, 20 and 21 or the maximum switching stage can be switched on at a time.

A vacuum gauge 27 is provided on the desk panel 11. It has an adjustable electric contact and is connected to the suction line system by means of a conduit 2S.

Signal lamps

29, 30, 31, 32 and 33 are provided on the desk panel 11and coordinated with the switches 14, 15, 16, 17 and 26; the lamp 29 indicates the minimum suction effect, the lamp 30 lights up when the switching stage I is switched on, the lamp 31 lights up when the switching stage Il is switched on, the lamp 32 lights up when the switching stage Ill is switched on and the lamp 33 lights up when the maximum suction elect is switched on by means of the switch 26 or when the contact of the vacuum gauge 27 closes.

Hand-

adjustable needle valves

34, 35, 36 and 37 are arranged in the

branch conduits

22, 23, 24 and 25 on the downstream side of the

magnetic values

18, 19, 2t) and 21. These needle valves are adjustable by means of hand wheels 38, 39, and 41 so that air can be admitted from the atmosphere to the

respective branch conduits

22, 23, 24 and 25 until a maximum suction effect of practically 0 atm. is obtained by the adjustment of the needle valve 34, of 0.2 atm. or 0.3 atm. by the adjustment of the needle valve 35, of 0.4 atm. or 0.4 atm. by the adjustmentl of the needle valve 36, and of 0.6 atm. or 0.8 atm. by the adjustment of the needle valve 37; consequently all vacuum intermediate values between 0 atom. and -1 atm. can be adjusted.

The apparatus is so designed that the suction effect in the pelotte 1 is obtained quickly or slowly while the switching stages I, II and HI are operative and when adjusted to the minimum and maximum switching stage. For this purpose an air tank 43 is connected to the hose conduit 5 by a branch conduit 42 so that the pump 8 sucks air simultaneously out of the hose conduit 5 and the air tank 43. Switching to rapid and slow suction can be eifected by means of a push-button tumbler switch 44 with which a magnetic valve 45 and a needle valve 46, adjustable by means of a hand wheel 47, are coordinated in the branch conduit 42. A lamp 48 arranged on the desk panel 11 lights up when the apparatus is switched to rapid and a lamp 49 lights up when the apparatus is switched to slow.

The apparatus is operated in the following manner:

(l) The main switch 10 is switched on; the lamp 12 lights up.

(2) The push-button switch 14 (minimum switching stage) is depressed; the lamp 29 lights up. After the stage for attaining a minimum vacuum and the switching stages I, Il and lll have been adjusted by means of the

hand wheels

38, 39, 49 and 41 of the

needle valves

34, 35, 36 and 37, for example, stage I having been adjusted by the hand wheel 39 to the range of 0.2 to 0.3 atm., stage II by the hand wheel 40 to the range or" 0.4 to 0.5 atm., and stage II by the hand wheel 41 to the range of 0.6 to 0.8 atm., the apparatus is ready for use. The hand wheel 47 is adjusted according to the desired suction speed.

(3) The pelotte 1 is placed on the childs head. Stage I is switched on by means of the push-button switch 15; the lamp 313 lights up.

(4) After for example 2 to 3 minutes have elapsed, stage Il is switched on by means of the push-button switch 16, the push-button switch 15 automatically springing back into its inoperative position. At the same time the lamp 30 goes out and the lamp 31 lights up.

(5) After a further short time interval has elapsed, stage Ill is switched on by means of the push-button switch 17, the push-button switch 16 automatically springing back. At the same time the lamp 31 goes out and the lamp 32 lights up.

(6) Now the extraction of the child from the womb takes place. onto stage ll or stage I. When the labour-pains commence, the apparatus is again switched onto stage III and the extraction continued.

The employment of the maximum vacuum may be necessary in exceptional cases. The push-button switch 25 is dien depressed; at the same time the lamp 33 lights up. In the case of acute danger occurring which demands the sudden interruption of the vacuum in the suction pelotte 1, the push-button switch 14 is depressed; air is admitted from the atmosphere to the suction system and the vacuum returns rapidly to 0 atm.

By means of the push-button tumbler switch 44 it is possible to switch to rapid or slow, as may appear advisable, whereupon the

lamp

48 or 49 lights up.

(7) After the extraction has been completed, the apparatus is switched to 0 atm. and then the main switch 10 is switched olf. ln the simpliiied form of construction of the apparatus illustrated in FIG. 2, a multiway-cock is employed instead of the

magnetic valves

1S, 19, 20 and 21 of the apparatus according to FIG. l. Furthermore, the air tank 43 with the magnetic valve 45 and needle valve 46 coodinated therewith can be dispensed with.

The hose conduit 5 extending from the handle 3 and having a vacuum gauge 59 leads via the vacuum vessel 5 to the suction pump 8 driven by the electric motor 7.

Branch conduits

51, 52, 53 and 54 are connected to the hose conduit 5 and lead to a common multiway-cock55 with a plug which has a central bore 56 one end of which leads into the atmosphere while the other end is adjustable If advisable, it is possible to switch back to one of the branch conduits `51., 52, 53 and 54 by means of a hand wheel 57 (see also FIG. 3). The

branch conduits

51, 52, 53 and S4 are so dimensioned that they enable different suction intensities in the hose conduit 5 and the suction pelotte 1 to be adjusted, the branch conduit 5,1 corresponding to the stage of minimum vacuum, the branch conduit 52 to the switching stage I (0.2 atm. to 0.3 atm.), the branch conduit 53 to the switching stage II (0.4 atm. to 0.5 atm), and the branch conduit 54 to the switching stage III (0.6 atm. to 0.8 atm.). For the maximum vacuum switching stage no branch conduit of the hose conduit 5 is provided; in the case of this adjustment all of the

branch conduits

51, 52, 53 and 54 are closed. In the branch conduits 51, 52., 53 and 54

needle valves

62, 63, 64 and 65, adjustable by means of hand wheels 5S, 59, 60 and l61, are arranged which, with normal adjustment, eect the sucking of air from the atmosphere into the hose conduit 5 until the maximum vacuum values of practical-ly atm., 0.2 atm. or 0.3 atm., 0.4 atm. or 0.5 atm. and 0.6 atm. or 0.8 atm. are reached, and enable the adjustment of the vacuum in the intermediate ranges between these values from 0 atm. to -1 atm.

Signal lamps may be coordinated with the switching stages I, II and IIIV and the minimum and maximum vacuum stages, as in the apparatus illustrated in FIG. 1, which, when they light up, indicate the stage actually switched on.

A foot-switch arrangement may be provided for the apparatus shown in FIG. 1 instead of the arrangement for the manual operation thereof. A foot-switch 66 illustrated in FIGS. 4 and 5 has tive mutually locked pushbutton switches 67, 68, 69, 70 and 71 for electrically transmitting the switching operations to the apparatus, which switches are coordinated with the switching stages I, II and I-II and the minimum and maximum vacuum stages and take the place of the push-button switches 14, 15, 16, 17 and 26 of the apparatus shown in IFIG. l.

FIGS. 6 and 7 show a foot-operated tumbler switch 72 which may be provided instead of the foot-switch 66 and has a plate-shaped pedal or rocker 73 to be actuated by the foot instead of the individual push-button switches for the switching stages. The rocker 73 can actuate switching contacts 75 by means of a lever system 74.

FIGS. 8 and 9 show a foot-operated switch 76 for the -apparatus illustrated in FIG. 2. The multiway-cock 55 shown in FIG. 3, to which the

branch conduits

51, 52, S3 and 54 are connected, is arranged in the switch 76 and its plug is rotatable by means of a plate-shaped pedal or rocker 77 actuated with the foot. Instead of the hand wheel 57 a disc 79 is arranged on a shaft 78 of the cock plug, which disc has apertures 80, corresponding to the individual switching stage positions, in which a locking device 81 consisting of a resiliently mounted ball or the like can engage and arrest the switch in the actually adjusted position.

Instead of a switch actuated with the foot, a live-pole rotary selector switch may be used which is arranged on the hose conduit and enables the apparatus to be remote controlled by hand. This switch has a removable setting knob capable of being sterilized.

The apparatus according to the invention, in order to render it independent of any operation by hand or with the foot after it has been switched on, may have an additional switching device working with time relays or time switches and automatically controlling the entire switching operation for the vacuum stages according to a set time table. This automatic controlling or switching device for switching in and out the vacuum stages I, II and III and the minimum vacuum stage is arranged following the push-button switches of the apparatus so that the automatic s-witching device can be rendered inoperative at any time by actuating the push-button switches 14, 15, 16 and 17. The selection of the time intervals between the inmatic switching device so that, for example, the suction pelotte, when the minimum vacuum stage is switched on, can be placed on the childs head, whereupon, on a switching element being actu-ated, the further switching operations of the individual vacuum stages take place automatically, for example so that stage I is switched on for a few seconds to 5 minutes, whereupon stage II is automatically switched on for a few seconds to 5 minutes, and tin-ally stage III for the extraction of the child. After the extraction has been completed, the entire apparatus is switched off by actuating a switching element.

I claim:

l. A vacuum extraction pump arrangement for childbirth in combination with extraction means, said arrangement comprising -a motor-driven vacuum pump, a main vacuum conduit in which the vacuum level is to be selectively determined and maintained, one end of said main conduit being connected to said vacuum pump and the other end of said main conduit being connected to said extraction means, said extraction means being adapted for engagement with the head of a child during child-birth, a plurality of parallel branch conduits connected at one end to said main conduit, adjustable -air bleed means in each of said branch conduits to adjust the amount of air permitted to bleed into said main conduit and the vacuum level maintained therein, each of said air bleed means having a hand-adjustable needle valve for tine adjustment, and controlling means in each branch conduit for selectively rendering the individual branch conduits operative to determine the vacuum level therein.

2. Pump arrangement for vacuum extraction apparatus as claimed in claim l, wherein the controlling means for adjusting the apparatus to different vacuum levels is constructed as electropneumatic controlling means.

3. Pump arrangement for vacuum extraction apparatus as claimed in claim 2, wherein the controlling means for adjusting the apparatus to different vacuum levels comprises magnetic valves which are arranged in each of the branch conduits, and push-button switches coordinated to the magnetic valves and provided with a mutual locking mechanism.

4. Pump arrangement for Vacuum extraction apparatus as claimed in claim 3, wherein a set of signal lamps is coordinated with the push-button switches, the signal lamps lighting up upon the operation of one of the pushbutton switches.

5. Pump arrangement for vacuum extraction apparatus as claimed in claim 3, wherein an additional switching arrangement is provided for the apparatus for controlling all the switching operations of the apparatus according to a previously set time table, the switching arrangement being arranged following the push-button switches and rendered inoperative by the push-button switches.

6. Pump arrangement for vacuum extraction apparatus as claimed in claim l, wherein the controlling means for adjusting the apparatus to diierent vacuum levels is constructed as purely mechanical controlling means.

7. Pump arrangement for vacuum extraction apparatus as claimed in claim 6, wherein the controlling means for adjusting the apparatus to different vacuum levels comprises a multiway-cock to which the branch conduits of the hose conduit are connected.

8. Pump arrangement for vacuum extraction apparatus as claimed in claim 7, wherein the multiway-cock has a plug which has a central bore communicating with the atmosphere, and a hand wheel is provided by which the bore is adjustable to one of the branch conduits.

9. Pump arrangement for vacuum extraction apparatus as claimed in claim 7, wherein a set of signal llamps is coordinated to the multiway-cock and serves to indicate the position of the multiway-cock.

l0. Pump arrangement for vacuum extraction apparatus as claimed in claim 7, wherein the multiway-cock is constructed as a foot-switch arrangement, a foot pedal is arranged on the foot-switch arrangement for switching the multiway-cock to one of the branch conduits of the 7 hose conduit, and a locking device is arranged in the footswitch arrangement for holding the foot-switch arrangement in the position actually adjusted.

11. Pump arrangement for vacuum extraction apparatus as claimed in claim 7, wherein an additional switching arrangement is provided for the apparatus for controlling all the switchingk operations of the apparatus according to a previously set time table, the switching arrangement being arranged following the multiWay-cock and rendered inoperative by the multiway-cock.

l2. Pump arrangement for lvacuum extraction apparatus as claimed in claim 1, wherein the needle valves have hand wheels.

13. Pump arrangement for vacuum extraction apparatus as claimed in claim 1, wherein for the selective rapid and slow suction to produce the vacuum, an air vessel is provided which is connected up with the hose conduit by an additional branch conduit, a needle valve -with a hand Wheel and a magnetic valve are arranged in said branch conduit and a push-button tumbler switch is coordinated to said magnetic valve.

14. Pump arrangement for vacuum extraction apparatus as claimed in claim 13, wherein two signal lamps are coordinated ywith the push-button tumbler switch for switching the apparatus for slow and rapid suction, and another signal lamp is arranged to indicate the switching on of the current supply and a further signal lamp is arranged to indicate the maximum Vacuum and can be actuated by means of an adjustable contact in a Vacuum gauge which is connected up with the hose conduit.

15. Pump arrangement for vacuum extraction apparatus as claimed in claim 1, wherein a recording device is connected up with the apparatus for recording the successive levels of vacuum during an extraction.

16. Pump arrangement for vacuum extraction apparatus as claimed in claim 1, wherein the controlling means is 'arranged to be -actuated by means oi a foot-switch arrangement.

17. Pump arrangement for vacuum extraction apparatus as claimed in claim 15, wherein the foot-switch arrangement comprises a foot-switch, a push-button switch being arranged in the foot-switch for each of the Vacuum levels and for minimum and maximum vacuum levels, the push-button switches being arranged to transmit switching impulses Via an electric circuit, and a locking device provided for mutually locking the push-button switches in relation to each other.

18. Pump arrangement for vacuum extraction apparatus as claimed in claim 15, wherein the foot-switch arrangement comprises a foot-operated tumbler switch, a foot pedal being arranged on the tumbler switch, and switching contacts being coordinated to the vacuum stages and the -levels for minimum and maximum vacuum, the f foot pedal on Vbeingldepressed actuating each ltime one of the switching contacts.

References Cited in the tile of this patent UNITED STATES PATENTS 974,286 Matchette et al. Nov. 1,1910 2,194,989 Torpin Mar. 26, 1940 2,439,515 Hodgson Apr. 13, 1948 2,449,217 Graham Sept. 14, 1948 2,702,038 Uddenberg et al. Feb. 15, 1955 2,781,041 Weinberg Feb. 12, 1957 2,907,345 Randall Oct. 6, 1959 2,998,256 Tipkins Aug. 29, 1961 FOREIGN PATENTS 101,841 Australia Aug. 13, 1937

Claims

1. A VACUUM EXTRACTION PUMP ARRANGEMENT FOR CHILDBIRTH IN COMBINATION WITH EXTRACTION MEANS, SAID ARRANGEMENT COMPRISING A MOTOR-DRIVEN VACUUM PUMP, A MAIN VACUUM CONDUIT IN WHICH THE VACUUM LEVEL IS TO BE SELECTIVELY DETERMINED AND MAINTAINED, ONE END OF SAID MAIN CONDUIT BEING CONNECTED TO SAID VACUUM PUMP AND THE OTHER END OF SAID MAIN CONDUIT BEING CONNECTED TO SAID EXTRACTION MEANS, SAID EXTRACTION MEANS BEING ADAPTED FOR ENGAGEMENT WITH THE HEAD OF A CHILD DURING CHILD-BIRTH, A PLURALITY OF PARALLEL BRANCH CONDUITS CONNECTED AT ONE END TO SAID MAIN CONDUIT, ADJUSTABLE AIR BLEED MEANS IN EACH OF SAID BRANCH CONDUITS TO ADJUST THE AMOUNT OF AIR PERMITTED TO BLEED INTO SAID MAIN CONDUIT AND THE VACUUM